recovery: Fix adb backup/restore

Communication with adb is now done via stdin/stdout.  Dupe these
descriptors and use them for read/write, and redirect the actual
stdin/stdout to the recovery log file.

Also limit progress updates to once per second to avoid overrun
on the messages socket, and silence some debug output.

Change-Id: I674fc9c38d94ea411f4ec5b271ed7a977c31aa93